Sheet material



Patented June 19, 1945 SHEET MATERIAL William August Hoflman and Richard Seyiarth 1 Schreiber, Wilmington, DeL, assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August 22, 1942, Serial No. 455,779

Claims- (Cl. 117-144) This invention relates to non-fibrous regenerated sheet wrapping material, and especially to bundles comprising this type of material in contact with fibrous products such as paper, cloth, etc. More particularly, it appertains to packages comprising cellulosic fabrics wrapped in Cello- Phane.

One of the newer sheet wrapping materials comprises essentially a thin non-fibrous regenerated 'cellulosic sheet (film, foil, pellicle, skin, structure, tissue, web) about 0.001 inch thick. Typical procedures for the manufacture of such products are disclosed in U. S. A. Patents 1,548,864, (Brandenberger) and 2,123,883 (Ellsworth).

Heretofore, it has not been practical to use the sheet wrapping material so produced for wrapping cotton fabrics, such as bed sheets, pillow cases and the like. If these were so wrapped, the wrapper rapidly developed a. horny, brittle character and split oif the wrapped object in a short time. Tremendous sums of mone and unbelievable amounts of time have been spent over at least a score of years in efforts to adapt regenerated cellulose sheet to this field.

The primary object of this invention was to treat regenerated cellulose sheet in such a way that it would not become brittle and break when wrapped about cotton textiles. Attendant objects were to provide a new and improved rigid (as opposed to limpness) and highly durable sheet wrapping material, and to produce an age-resistant regeneratedcellulosic film.' Other objects were to devise ways of producing a long lasting softened Cellophane, to discover means enabling cast regenerated cellulose webs to maintain their flexibility for long periods of time, and to find ways of restraining or obviating the embrittlement of non-fibrous cellulosic pellicles. Another object was to provide a firm flexible, non tacky transparent highly stable cellulosic pellicle containing a very high proportion of a non-migrating, non-volatilizing monomeric adjuvant. A general advance in the art, and other objects which will appear hereinafter, are also contemoxides) to be similarly useful in the manner described in detail hereinafter.

How the foregoing objects and related ends are accomplished will be apparent from the following exposition, in which are disclom the principal and divers embodiments of the invention, including the best modes contemplated for carrying out the same.

Parts are given by weight throughout the application, unless otherwise specified.

Example] Extrude viscose and form a continuous web of regenerated cellulose in the manner described in U. S. A. Patent 1,548,864. In the bath or casting machine vat, preceding the drier, incorporate 11%, based on the weight of the bath, of the methanol adduct of zzfi-dihydrotbiophene-lzi-dioxide having the structural formula:

Example [I Repeat Example I, but omit the glycerol from the casting machine vat. A transparent and flexible sheet product of similar durability will be obtained. The durability of the sheet material, when wrapped about a cotton fabric such as a bed sheet, will be as great as that of the product of Example I.

Example III Extrude viscose into a bath comprising sulfuric acid and sodium sulfate. Regenerate the resulting coagulated film. Desulfur, bleach and wash the coagulated film in the manner described in U. S. A. Patent 1,548,864. Before drying, pass this gel film through an 11% aqueous solution of the methanol adduct of 2:5-dihydrothiophenelzl-dioxide maintained at 30 C. Regulate the speed of the film so that it remains in the solution long enough for its gel structure to be thoroughly impregnated. Remove the excess liquid from the film, after it emerges from the solution, with doctor knives, and dry to a 6% moisture content (the atmospheric equilibrium quantity) on a conventional drier. The dry film will contain 20% of the sulfone, based on the weight of the cellulose, and have great durability in addition to being flexible and transparent.

Example IV Pass film, produced as in Example III, through a bath containing 30% of the methanol adduct of 2 5-dihydrothiophene-l ldioxide. Remove the excess solution from the surface of the film, and dry in the customary manner. The resulting film will contain 45% of the sulfone. It will not be limp or tacky. It will lend itself particularly well to wrapping operations. It will have tumbling (drop) values (see definition in U. S. A. Patent 2,275,348) of 200, as compared with the value of 80-85 which is exhibited by the non-fibrous cellulosic film employed in ordinary commercial practice. No practical change in properties or composition of the film, after long contact with cotton textiles and like fibrous cellulose materials, will be found.

Example V Prepare film in the manner described in Example II, but replace the methanol adduct of .2r5-dihydrothiophene-1:l-dioxide with the corresponding ethanol adduct. Essentially the same quality of non-fibrous cellulosic film will be obtained.

Example VI Example VII Prepare continuous regenerated cellulose sheet in the manner described in Example III,

but utilize a final bath containing 11% of the methanol adduct of 2:5-dihydrothiophene-1:1 dioxide and 11% glyceroL- The dried sheet will contain 18.5% of the methanol adduct and 23.5% of glycerol. It will be very smooth, flexible, highly durable, and show tumbling values of 572 as compared with the value of 80 as shown by commercial sheets of regenerated cellulose.

Example VI I I Prepare a web of regenerated cellulose in the manner described in Example III, and pass through a bath containing 11% of the addition product of ethylene glycol and 2:5-dihydrothiophene-lzl-dioxide having the formula:

Remove the excess treating solution and dry in the usual manner. The resulting web material will be transparent and flexible and maintain these characteristics even when in contact with fibrous cellulosic bodies.

The ethylene glycol 2:5-dihydrothiophene- 1:1 -dioxide addition product may be prepared according to the general procedure disclosed in U. S. A. Patent 2,219,006.

Example IX Prepare a web of regenerated cellulose in the manner described in Example III, and pass through a bath containing 11% of the addition product of glycerol and 2:5-dihydrothiophenelzl-dioxide prepared by the general procedure described in J. S. A. Patent 2,219,006. Remove the excess treating solution and dry in the usual manner. The resulting sheet material will be transparent and flexible and maintain these characteristics even when in contact with fibrous cellulose bodies.

Example X Cast, desulfur, bleach and wash regenerated cellulosic web in the conventional manner, passing this gel materialthrough an aqueous bath containing 7% beta-ethylsulfinyl tetramethylene cyclic sulfone having the formula:

and dry in the usual manner. The resulting film will be clear, highly durable and characterized by the permanence of its physical characteristics when in contact with fibrous cellulosic materials.

This sulfone may be prepared by reacting ethanethiol with 2 5-dihydrothiophene-1 ldioxide in the manner described in U. S. A. Patent 2,219,006, followed by oxidation of the resultant product with 30% hydrogen peroxide.

Example XI Prepare regenerated cellulose sheet in the manner previously described, and impregnate it by immersing it in a solution containing 11% of 3 4-dimethoxy-tetrahydrothiophene-l l-dioxide. Remove excess solution from the surface of the sheet and dry the same in the usual manner. The resulting sheet will be clear, soft and durable.

This sulfone, having the formula:

Hz-CH-O-CHa may be prepared by reacting 2*:5-dihydrothiophene-lzl-dioxide with a chlorinating agent consisting of chlorine and absolute methanol at 0 C. to produce the intermediate, 3-chloro-4 methoxy tetrahydrothiophene-lzl-dioxide, and thereafter subjecting said intermediate to the action of methyl-alcoholic potassium hydroxide in equivalent amounts to produce the compound used in the aforementioned treatment. The final product may be isolated by recrystallization from methanol.

Example XII Prepare film as described in Example III, impregnate it with an aqueous solution containing 11% of diethylsulfone. Remove the excess solution by means of doctor knives and squeeze rolls and dry the film by passage over heated rolls. The resulting film will be clear, soft and durable.

The diethylsulfone may be prepared by reflux ing diethyl sulfide with an excess of 30% hydrogen peroxide over a period of 5 hours. The excess peroxide may be decomposed and the desired product isolated by evaporation of the solution on a steam bath. Purification of the product may be accomplished by recrystallization from ethanol orby distillation under reduced pressure.

Example XIII Prepare gel film as described in Example III. Impregnate by immersion in an aqueous bath containing 11% of 2:5-dihydrothiophene-l:1- dioxide (for preparation, see German Patent 506,839), having the formula:

Remove excess solution from the surface of the film and dry by passing over hot rolls in the customary manner. The film so produced will be flexible, transparent, highly durable and contain 19% of the sulfone. The sheet will retain its superior durability characteristics at least four times as long as the film produced according to U. S. A. Patent 1,548,864.

Erample XI V Extrude-viscose in the form of a tube (see U. S. A. Patent 2,141,776) and coagulate, regenerate and purify the resultant cellulose pellicle in the manner previously described for continuous webs. Pass the gel tubing through a bath containing 11% of the methanol adductof 2:5- dihydrothiophene-lzl-dioxide. Remove excess impregnating liquid from the surface of the tube. cut the same into appropriate short lengths and apply the sections to the mouths and near neck portions of liquor bottles as secondary closures.

Upon evaporation of the moisture each band (tube section) will shrink into intimate contact with the neck of the bottle and the primary closure over which it has been placed, and serve to protect the same until the time of willful removal. If there is a paper revenue stamp over the stopper (cork Or the like) and adjacent neck portion of .the bottle, it will be found that the cellulosic band is not embrittled by contact therewith even after long periods of storage. It follows that the premature secondary closure removal frequently caused by such combinations in this field will be obviated.

Example XVI .Extrude viscose in sheet form into a sulfuric acid-sodium sulfate coagulating and/or regenerating bath. Desulfur, bleach and wash in a continuous manner according to the teachings of U. S. A. Patent 1,548,864. Before drying draw the web through an aqueous bath, maintained at a temperature of 30 C. and containing 11% of di-beta-hydroxy-ethylsulfoxide.- Proportion the bath so that the sheet will be thoroughly impregnated. Remove excess liquid from the impregnated gel structure and dry on the conventional roll drier. The finished sheet will contain 24.8% of the sulfoxicle and approximately 6% of water. It will be transparent, flexible and durable. It will show no embrittlcment after 5 days intimate contact with paper or cotton tabric. There will be no noticeable change in properties or composition of the sheet over long periods of time.

The sulfoxide may be prepared by oxidizing commercially available di-(beta-hydroxyethyl) sulfide with a 30% solution of hydrogen peroxide at a temperature of 70 C. Isolation may be brought about by destroying the excess peroxide when oxidation to the sulfoxide is completed. Satisfactory recrystallization may take place from ethanol or water.

Example XVII Prepare film as described in Example Ill. Im-

pregnate it with 2:2'-(methylene disulfinyl-) diethanol having the formula:

o=s-cH,-ou,-0n

(1H2 o=s' cH,-'cn,oH

from a 7% aqueous solution. Dry the impregnated film according to the customary procedure. The resulting film will be soft and durable and characterized by permanence of its composition and physical characteristics. v

The sulfoxidate may be prepared by reacting 2 mols of thioethylene glycol with 1 mol of formaldehyde in the presence of acidic catalyst and oxidizing the resulting product by means of 30% hydrogen peroxide solution. Purification is brought about by recrystallization from ethanol or methanol.

Example XVIII Prepare gel film as described in Example III. Impregnate it with ethyl-gamma-hydroxypropy1 sulfoxide from a 7% aqueous bath. Remove excess solution and dry as usual. The pellicles so produced will contain about 15% of the sulfoxide and be flexible, transparent and durable.

This sulfoxide, having the formula:

may be prepared by reacting ethanethiol with allyl alcohol in the presence of mercuric acetate catalyst according to the method of Kaneko, J. Chem. Soc. Japan 59, 1139, (1938) followed by oxidation of the resulting product by means of a 30% solution of hydrogen peroxide.

Example XI X Prepare film as described in Example III. Suspend the gel material in an aqueous bath containing 10% of ethyl- :3-dihydroxypropyl sulfoxide having the formula:'

on 0=s0H1cHcn2 oH urn-cut Remove excess solution and dry in the usual manner. The resulting flexible. transparent sheet material will maintain its durability when in contact with cellulosic materials such as cloth and paper.

This sulfoxide may be prepared by reactingethanethiol with glycerol chlorohydrin in the presence of an alkaline reagent. The intermediate so produced may then be oxidized by means of a 30% hydrogen peroxide solution. The final product can be purified by recrystallization from ethanol.

Example XX Prepare regenerated cellulose web as described in Example III. Immerse and impregnate in an aqueous bath containing 11% of methylbutyl sulfoxide. After removal of excess solution, dry by the customary procedure. There will be obtained a highly durable transparent sheet suitable for wrapping fibrous cellulosic materials.

The methylbutyl sulfoxide may be prepared through the action of methyl chloride on butanethiol under alkaline conditions followed by oxidation of the product with a 30% solution of hydrogen peroxide.

Example XXI o o I II I I II I C--SC and (,-S-C I I I II I respectively. These compounds comprehend open chain, closed ring, or both, configurations. The corresponding general formulae, equivalent to the generic term sulfoxidate, are:

in which n represents a number from the group consisting of 1 and 2, and R, R1, R2 and R3 represent identical or. different straight or branched chain organic radicals in which there is a carbon atom directly attached to the sulfur atom. The compounds may contain one or more of the sulfoxide or sulfone linkages and where there are more than one, they may be alike or different. Preferably the Rs are organic radicals, or more specifically, hydrocarbon residues containing water solubilizing substituents.

There appears to be no chemical or structural limitation on the operability of the compounds having the foregoing formulae (sulfoxides and sulfones), but they must be water soluble, that is,

'dissolvable in water to such an extent that the can be incorporated in the non-fibrous cellulosic structure from an aqueous bath. In the interest of exactness, it is pointed out that a compound is considered waten soluble if 2% will dissolve in water at a temperature not greater than C. Adequate water solubility may be conferred on the compound by the presence of substituents and linkages such as the conventional solubilizing groups, -OI-I, -O-alkyl (alkoxy), -NH2, -COOH, -SO3I-I, -NH-, -CO-, -CO-NH-, etc, as exemplified by the group of radicals in the compounds of the examples and the tabulation following. In

- general, hydroxyl and ether radicals insure sufficient water solubility for the purposes of this invention.

In addition to the compounds utilized in the specific examples, amplification of the invention may be made by mentioning other suitable addition or impregnating compounds, such as:

HO-CHz-CHz-SQ-CH2-CH2SO-CHz-CH2-OH HO-CHz-CH2-SOz-CHz-CH2-SO2-CH2-CH2-OH Cal-Is-SO-CHz-CHz-SO-CzHs CzHs-SOz-CHz-CI-Iz-SOz-CzI-Is CHz-CHz-SOZ CHz-CH:

The invention comprehends chemically any non-fibrous cellulosic pellicle which may be obtained by the coagulation and/or regeneration from an aqueous (or aqueous-alkaline) cellulosic dispersion (or solution). In addition to regenerated cellulose obtained from viscose (solution of cellulose xanthate) and from other materials, as in the cuprammonium process, cellulose ethers, precipitated from aqueous solutions or dispersions, such as alkyl cellulose (preferably ethyl or methyl cellulose), glycolcellulose, cellulose glycolic acid and the like, may be treated satisfactorily. The specific cellulose substitution derivatives just mentioned are usually grouped under the generic term low (or lowly) substituted cellulose ethers. In the language of the art, low substituted cellulose derivatives are those in which there are not more than about one mol of substituent per glucose unit.

The invention contemplates, as a pellicle, any non-fibrous cellulose structure, particularly those physical forms such as sheet, artificial straw, artificial sponges, caps, bands, long tube, filament, yarn, etc.

The impregnation of the pellicle with the sulfoxidate has, for convenience, been described as a treatment of the same in the gel state .(the most practical mode of operation). If one desires, it is possible to re-wet a dried film and, when the same is highly swollen, treat it with a sulfoxidate bath similar to those described above.

In some cases it may even be desirable to spray the sulfur-oxygen compound on to a film.

The film, in which the oxysulfide is incorporated, may or may not have present therewith the conventional regenerated cellulose softeners, such as glycerol, glycol, formamide, glycolpolyformal, N-(2:3-dihydroxypropyl) hydroxy acetaphene-lzl-dioxide with methyl butyl su1foxide.

For ordinary uses, the preferred concentration of the sulfoxidate in the aqueous bath is from 4% to Gel regenerated cellulose ordinarily contains about 300% (based on the weight of the cellulose) of water. Upon drying, the concentration of the sulfoxidate will, therefore, generally be increased about three-fold. The strength of the impregnating bath is governed to some extent by the length of the time available for the impregnating operation. If time is available for reaching an equilibrium between the bath and the film, the concentration of the sulfoxidate (in the bath) can be lower than in those cases where the sheet is removed from the bath before it has taken up the maximum (equi librium) amount of impregnating solution of which it is capable. The temperature of the bath also has some influence on the concentration. Preferably the bath is operated at 25 to 30 C.

Finished sheet material containing sulfoxidate in the range 1% to 50% are useful in specific fields. Impregnating solutions containing at least 30% of the adjuvant may be necessary to insure 45% to 50% in the final film. The bulk of the film produced will contain about 15% of the sulfoxidate.

If a colored cellulosic sheet is desired, it may be obtained in any of the ways commonly known in the art, including the passage of the sheet material through a bath containing a suitable dye. If desired, the dye may be added to the bath introducing the sulfoxidate. I Film containing the sulfoxidate may be subjected to any of the customary after-treatments such as sizing, coating or the like.

Many of.the advantages of the present invention will be apparent from the foregoing. Some, which are especially important however, should be pointed qut more specifically. It is possible to prepare film containing more than 40% and even up to 60% of the sulfoxidates of this invention that is remarkably free from tackiness. The films produced according to this invention show excellent adhesion to moistureproofing coatings, and their durability compared with the standard films now available is extraordinary, as

shown, in one way, by the tumbling values which may be increased more than seven-fold over the tumbling values of common types or" Cellophane.

The permanence with which the sulfoxidates remain in the non-fibrous cellulosic structure is unique. Sofar as is known, this is the first nonvolatilizing, non-migrating monomeric adj uvant material for this type of thin sheet material. Heretofore it has not been considered possible to incorporate more than 10% to 20% of glycerol and the like in Cellophane without producing an undesirable ta'ckiness and poor adhesion for moistureproofing coatings. As evidenced by Example VII, the presence of 18.5% of a sulfone of this invention enables the glycerol content to be raised to 23.5% without undesirable surface characteristics being produced. A material of the type described in Example IV, containing 45% of the methanol adduct of 2 5-di-hydrothiophene-1 ldioxide, has good adhesion for mois'tureproofing coatings. Even with high concentrations of sulfoxidates, sheet wrapping materials of this invention are highly durable, transparent and resilient,

and are not flimsy or tacky.

The material of this invention is remarkably well suited to operations requiring folding of the sheet. Such sheets are not quickly embrittled when used directly for wrapping fabrics, textiles, paper, etc. As a result, the distensibility and dutability of the original wrapper in such packages are retained, thereby greatly extending the life of the package.

As many apparently widely'difierent embodiments .of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

We claim: I

1. Regenerated cellulose sheet containing a water soluble organic sulfoxidate.

2. Regenerated cellulose sheet containing a water soluble sulfoxide.

3. Regenerated cellulose sheet containing a water soluble sulfon'e.

4. The process which comprises impregnating wet regenerated cellulosic sheet with a water soluble organic sulfoxidate whereby to form a nonfibrous sheet material particularly suited as a wrapping for cotton cloth and like fibrous cellulosic fabric.

5. Gel non-fibrous cellulosic sheet precipitated from an aqueous alkaline solution and containing a water soluble organic sulfoxidate.

- 6. Regenerated cellulosic sheet or tube containing 1% to Water soluble organic sulfoxidate. 7. Regenerated cellulose sheet containing from above 40% and up to 60% of a water-soluble organic sulfoxidate. 1

8. Regenerated cellulose sheet containing a CERTIFICATE OF CORRECTION.

Patent No. 2,378,1fl9. June 19, 191

WILLIAM AUGUST HOFFMAN, ET AL.

It is herehycertified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page L4,, second column, lines '72 and 75, strike out "filament, yarn,"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed andseale'd this 2nd day of October, A. D. 1916.

Leslie Frazer (Seal) First Assistant Commissioner of Patents. 

